How to place all selected vertices is same position in UV map?
Select them and scale them to 0.

Select the two vertices, then press s, then 0.

Because they are just points in space, this will not effect the verts, but it will put them in the same place, because the vector &quot;connecting&quot; them will be scaled to zero.

There is a better method however.

Select an island.
Set &quot;snapping&quot; mode to vertices.
Grab (g) and hold ctrl to snap.
Move all islands to the same location.



Tip; UV select mode to &quot;islands&quot;.



You can do something similar to multiple vertices at once by:

Moving them to relatively the same position. (l and g).
Select all (a).
Open the specials menu (w).
Choose &quot;Remove Doubles UV&quot;



If you have LOTS of islands!
As a final workaround method, if you have LOTS of islands, you can use this scaling hack. It is not technically a &quot;good&quot; method, but it works. The goal of this method is to scale everything down to one point, then blow it back up. To be able to blow it back up, we need to leave some geometric data, so we can't actually scale to 0.

Select all (a).
Select &quot;Median Point&quot; from the Rotation/Scaling Pivot menu.
Scale to a very small number (s, 0.0001, Enter).
Select &quot;Individual Origins&quot; from the Rotation/Scaling Pivot menu.
Scale the islands back to their original size (s, 10000, Enter).

The islands should now all have approximately the same origin. You can move them to your desired location.